At any given moment, only one or two seats are available at the lowest discount fare.

Fodors says if you book more than two seats, all of them will be bumped up to the next highest fare.

Semier learned that too late.

"I did a little bit of research and found that there were only three tickets available at that price," he aid. "Once I went to the fourth ticket, then they raised the price to $789 each for all four tickets."

How to Protect Yourself

The travel website ParkSleepFly.com says in order to avoid this, you should check carefully before you click the purchase button.

If it bumps up everyone's fare, the site says consider booking each ticket separately.

Semier complained to Delta. They later agreed to give him a credit for what he overpaid toward his next vacation.

A Delta spokesman confirmed what he found, telling us "airline fares can be affected by a variety of factors, including number of seats available within a particular fare class." (See below for full Delta statement)

Bottom line: Check before you click so you don't waste your money.

_______________________________

Don't Waste Your Money is a registered trademark of the EW Scripps Co.

"Airline fares can be affected by a variety of factors, including number of seats available within a particular fare class for people traveling on the same itinerary; the cost of providing the service; the cost of jet fuel; time and date of purchase; the route flown; and the fare class purchased. Delta offers a wide range of fares for leisure and business travelers, and our best fares are always available at delta.com.

To ensure our customers have the best information available from delta.com, we offer our Best Fare Guarantee as well as a 24-hour Risk-Free Cancellation policy."